It's not diseconomic, but it obviates a lot of constraints that required a person to manage a coordination problem, and those were a lot of jobs. Keynesian ideas about employment and GDP are just having an apocalypse. Like someone replaced the hole diggers and fillers with a conveyor belt and I would guess Keynes critics would have some predictive power here.

A couple developers can collaborate, but several need someone to specialize in coordination to yield additional value from more workers. Whether you call it management or orchestration, the need emerges at each threshold of additional complexity.

When AI collapses the productivity of 10 people into one, that's the disruption. The best AI user is going to suck all the opportunity out of the room for the others, and that's when layoffs happen. However, this assumes a fixed pie of opportunity. That's the real problem. As though there were only so much dirt to shovel.

FAANGs are old/mature and don't have exponential growth in front of them anymore, where opportunity within them is mainly about optimizing themselves but not growing in radical new directions. AI will indeed eat those optimization workforces alive. They resemble professions because law firms and doctors offices aren't growing either. They're mostly solving internal optimization problems, not finding net new growth opportunities.

The real effect is AI radically polarizing the difference between growing and dying in an org, where any firm that isn't growing fast enough will have its fixed opportunity pie collapse as AI disrupts this regulated oxygen supply. Whereas, growing firms without ceilings on the opportunity to deliver value will use AI to grow to the opportunity available.

Professionals can do fine if they re-orient themselves to new growth with different unit pricing, but yes, anything large and slow moving is probably going to get eaten.